Will there be faction changes?

I don't think this would be posssible becouse you could only make characters on same side. Adding services like this would break the whole faction identity thing.

Only true for pvp realms.

I think that with the way they intend to set up layering, faction transfers will probably only be a thing when the classic servers are shrinking to a point that transfers are needed (in the opposite way of how it was in vanilla).